Calcifying organisms such as benthic foraminifera are susceptible to changes in ocean pH and alkalinity. Responses to these changes include variations in mortality, calcification rates or assemblage composition, which have been observed in field and experimental studies. Here we applied a growth experiment with benthic foraminiferal propagules under different pH conditions to gather insights into the effect of pH on the composition of grown assemblages. A homogeneous propagule assemblage from a local mudflat in Corfu Island (Greece) was exposed to a range of pH conditions (6.5, 7.2, 7.8 and 8.5) for 5 weeks. In a second experiment, the assemblages were first exposed to low and subsequently to high conditions for a total of 8 weeks. After termination of the experiments, we recorded high survivability and growth throughout the treatments. Analysis of the assemblage composition of the first experiments revealed a shift from porcelaneous dominated taxa in the higher pH treatments to an assemblage with higher numbers of agglutinated taxa in the lower pH treatments. Soft-shelled monothalamous species were common throughout. The second experiment revealed assemblages that were significantly dominated by porcelaneous taxa with monothalamous taxa being almost absent. The results of this study are congruent with other observations on changing assemblage compositions with changing pH from both laboratory and field studies. The fast response of the assemblages through activation of potentially dormant propagules adds insights into the mechanisms behind seasonal composition changes in naturally variable environments such as river estuaries. They also shed new light on possible effects of continuous decreases in ocean pH on shallow-water foraminiferal assemblages in future.

钙化生物如底栖有孔虫易受海洋pH和碱度变化的影响。对这些变化的反应包括死亡率，钙化率或组合物组成的变化，这已在野外和实验研究中观察到。在这里，我们应用了底栖有孔虫繁殖体在不同pH条件下的生长实验，以收集有关pH对生长的组合物组成的影响的见解。将来自科孚岛（希腊）本地泥滩的均质繁殖体组合暴露于一系列pH条件（6.5、7.2、7.8和8.5）下5周。在第二个实验中，首先将组合物暴露于低水平，然后暴露于高水平的条件下，共8周。实验终止后，我们记录了整个治疗过程中的高存活率和生长。对第一个实验的组合物组成的分析表明，从较高pH处理中的以猪肉为主的分类单元向较低pH处理中具有较高凝集分类单元的组合转变。甲壳类软体动物在整个时期都很普遍。第二个实验揭示了组合，其中大部分以猪类为单位，而单孔类则几乎不存在。这项研究的结果与其他有关实验室和现场研究中随pH变化而改变组合物成分的观察结果一致。通过激活潜在的休眠繁殖体，组合的快速响应为洞察自然变化环境（例如河口）中的季节性成分变化背后的机理提供了见识。